1. Field of the Invention
This invention relates to beam addressable files and more particularly to a beam addressable file in which an amorphous magnetic composition having uniaxial anisotropy is used as the storage medium.
2. Description of the Prior Art
Beam addressable files using thin maagnetic films of insulators are known in the art. For instance, materials such as gadolinium iron garnets have been used. Also, metals such as MnBi have been used as the storage medium in beam addressable files. General descriptions of these file systems can be found in the following references:
1. A. H. Eschenfelder, J. APPL. PHYS., 41, 1372 (1970).
2. j. a. rajchman, J. APPL. PHYS., 41, 1376 (1970). PA1 3. r. e. mcDonald et al, J. APPL. PHYS., 40, 1429 (1969). PA1 4. d. chen et al, J. APPL. PHYS., 39, 3916 (1968).
In addition to these materials, stoichiometric MnAlGe has been suggested as a suitable material in a magneto-optic environment. This is a polycrystalline film, as are generally the magnetic films used for beam addressable file applications.
Some non-magnetic amorphous materials have been used in beam addressable file environments, as can be seen by referring to U.S. Pat. No. 3,530,441. These amorphous materials are "ovonic-type" materials which do not exhibit magnetic properties. They undergo structural changes when being switched in the beam addressable environment in contrast with the switching which occurs in a magnetic film. Because structural changes (transitions between an amorphous and a crystalline state) are much more destructive on the film itself, magnetic films can be switched many more times than presently used non-magnetic amorphous films in this type of environment.
Amorphous films have an advantage in that they can be placed on any type of substrate and can be adjusted to provide wide composition ranges. Additionally, the requirements relating to polycrystalline grain size which are present with crystalline beam addressable storage material are not present here.
It is desirable to provide an amorphous material which is suitable in a beam addressable file environment but which does not store information by a structural change in the physical properties of the material. Additionally, it is desirable to provide a magnetic storage medium in which domain size can be regulated and in which switching between various magnetization states is reversibly achievable over a great number of cycles.
Accordingly, it is a primary object of this invention to provide a beam addressable file having an amorphous magnetic film as the storage medium.
It is another object of this invention to provide a beam addressable file having as a storage medium a material whose magnetic properties can be easily changed over wide ranges.
It is still another object of this invention to provide an improved beam addressable file using a magnetic storage medium whose composition can be readily varied.
It is a further object of this invention to provide a beam addressable file using a magnetic storage medium which can be placed on any type of substrate, including both insulating and conducting substrates.